Sometimes, science surprises us. An ocean float we sent out to study the Totten Glacier in Antarctica took an unexpected detour. Initially, we were disappointed when it drifted away from its intended spot. But it ended up near ice shelves where no ocean data had ever been gathered before.
This float spent over two years drifting through remote waters, spending nine months beneath the Denman and Shackleton ice shelves. It sent back vital information about those regions, often hard to access. Understanding the ocean beneath these ice shelves is key to knowing how much Antarctica might contribute to sea-level rise.
Argo ocean floats are remarkable tools. They are free-floating devices that measure temperature and salinity as they rise and fall through the ocean, diving deep and then surfacing every ten days to send data to satellites. With 90% of the extra heat from climate change stored in oceans, they help us monitor global warming effectively.
Our float was deployed to study how ocean heat affects the rapidly melting Totten Glacier, which could potentially raise sea levels by about 3.5 meters. We knew warm water was reaching the base of the glacier, causing accelerated melting.
Though it drifted away from the Totten Glacier, it revealed valuable insights about the Denman Glacier, which has enough ice to contribute about 1.5 meters to global sea levels. Recent studies have shown that the Denman Glacier is at risk of instability, making the float’s findings crucial.
The Denman Glacier is vulnerable to warm ocean waters, which can melt the ice from beneath. Unfortunately, measuring these conditions is complicated. Although we can drill through ice to collect data, it’s costly and not frequently done. Thus, our float’s data provided the first measurements from beneath an East Antarctic ice shelf.
During its nine months beneath the ice, the float gathered temperature and salinity profiles every five days. Though it couldn’t communicate with satellites, it gave us hints about its location through collisions with the ice, allowing us to map its drift.
The findings revealed that the Shackleton ice shelf is currently less vulnerable because it isn’t exposed to warm water. In contrast, the Denman Glacier is susceptible to melting, indicating that even slight changes in water temperature could result in significant melting.
These observations confirmed that both the Denman and Totten glaciers are at risk from warm ocean water. Together, they hold enough ice to account for five meters of potential sea-level rise. While the West Antarctic ice sheet faces immediate threats, the East Antarctic ice, with its larger volume, is critical for understanding future sea levels.
If the ice retreats beyond its current position, both glaciers could dramatically shift into an unstable state. Once this process starts, reversing it would be nearly impossible. It could take centuries for sea levels to rise fully, but if that melting begins, we are committed to those changes.
Going forward, we need to deploy more floats around Antarctica. This will offer a clearer picture of how ice shelves respond to ocean changes and aid in better predicting future sea-level rises.
